Vibrational and UV spectra, first order hyperpolarizability, NBO and HOMO–LUMO analysis of 4-chloro-N-(2-methyl-2,3- dihydroindol-1-yl)-3-sulfamoyl-benzamide S. Muthu a,⇑ , T. Rajamani b , M. Karabacak c , A.M. Asiri d,e a Department of Applied Physics, Sri Venkateswara College of Engineering, Sriperumbudur 602105, Tamilnadu, India b Department of Physics, Global Institute of Engineering And Technology, Melvisharam, Vellore, India c Department of Mechatronics Engineering, H.F.T. Technology Faculty, Celal Bayar University, Turgutlu, Manisa, Turkey d Department of Chemistry, Faculty of Science, King Abdulaziz University, Jeddah, Saudi Arabia e Center of Excellence for Advanced Materials Research, King Abdulaziz University, Jeddah, Saudi Arabia highlights  Spectroscopic properties were examined by FT-IR and FT-Raman techniques.  The vibrations were assigned with PED.  NLO and NBO analysis of the title molecule were studied.  HOMO and LUMO energies and MEP distribution of the molecule were calculated.  Thermodynamic properties were investigated. graphical abstract article info Article history: Received 3 September 2013 Received in revised form 19 October 2013 Accepted 31 October 2013 Available online 8 November 2013 Keywords: DFT Vibrational analysis First order hyperpolarizability NBO and NLO analysis MEP abstract In this work, the vibrational spectral analysis was carried out by using FT-Raman and FT-IR spectroscopy in the range 4000–100 cm 1 and 4000–400 cm 1 , respectively, for 4-chloro-N-(2-methyl-2,3-dihydroin- dol-1-yl)-3-sulfamoyl-benzamide (C 16 H 16 O 3 N 3 SCl) molecule. Theoretical calculations were performed by density functional theory (DFT) method using 6-31G(d,p) and 6-311G(d,p) basis sets. The complete vibra- tional assignments of wavenumbers were made on the basis of potential energy distribution (PED). The results of the calculations were applied to simulated spectra of the title compound, which show excellent agreement with observed spectra. The frontier orbital energy gap and dipole moment illustrates the high reactivity of the title molecule. The first order hyperpolarizability (b 0 ) and related properties (l, a, and Da) of the molecule were also calculated. Stability of the molecule arising from hyperconjugative interactions and charge delocalization has been analyzed using natural bond orbital (NBO) analysis. The UV–vis spectrum of the compound was recorded in the region 200–400 nm in ethanol and electronic properties such as excitation energies, oscillator strength and wavelength were calculated by TD-DFT/ B3LYP method. Molecular electrostatic potential (MEP) and HOMO–LUMO energy levels are also con- structed. The thermodynamic properties of the title compound were calculated at different temperatures. Ó 2013 Elsevier B.V. All rights reserved. Introduction 4-Chloro-N-(2-methyl-2,3-dihydroindol-1-yl)-3-sulfamoyl-benz- amide (CMDS) is an oral anti-hypersensitive diuretic agent indi- cated for the treatment of hypertensive and edema [1]. Its molecule contains both a polar sulfamoyl chlorobenzamide moiety and a lipid-soluble methylindoline moiety. It differs chemically from the thiazides in that it does not possess the thiazide ring sys- tem and contains only one sulfonamide group. It is a white to yel- low-white crystalline. It is used to treat high blood pressure. Lowering high blood pressure helps prevent strokes, heart attacks 1386-1425/$ - see front matter Ó 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.saa.2013.10.115 ⇑ Corresponding author. Tel.: +91 9443690138; fax: +91 4427162462. E-mail addresses: muthu@svce.ac.in, mutgee@gmail.com (S. Muthu). Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy 122 (2014) 1–14 Contents lists available at ScienceDirect Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy journal homepage: www.elsevier.com/locate/saa